JP2003-306107A discloses a driving operation assisting system, which transmits information regarding an approaching status of a vehicle approaching the preceding vehicle to an operator using a haptic signal via equipment of the vehicle. The equipment is different from a device that the operator uses to control the driving of the vehicle, such as a steering wheel. According to this known system, the driver's seat moves to the rear immediately after a distance to the preceding vehicle becomes less than a predetermined value. One other driving operation assisting system transmits information on lateral position of a vehicle within a lane via haptic signals from a driver's seat.
Using the conventional systems, it is difficult for an operator to recognize an amount of risk from the preceding vehicle even though the approaching of the preceding vehicle can be clearly transmitted to the operator via reward motion of the driver's seat. Some systems attempt to transmit information of various different levels of risks to the operator via one or any combination of different pressing forces from different portions of the driver's seat. However, a need remains for an improved information conveyance that prompts an operator of a vehicle to perform an appropriate driving operation in response to different levels of risks as well as more intelligible conveyance of magnitudes of the risks to the operator.